Section 53(2)(b) in West Bengal Municipal (Building) Rules, 2007
(b)for ventilating water closet in bathroom, such water closet or bathroom or kitchen or any room not intended for human habitation, if not opening on to front open space, rear open space, side open space or interior open space, shall be opened up to a ventilation shaft, the size of which shall be as per provisions incorporated in Tables under rule 50;